Not seeing any issues with the autocomplete listbox in the Add-ons Manager. If you contact me with further details, I'd be glad to try to help. Preferably use the listed support forum or my contact form at http://www.shadetreeapiary.com/extension/Forms/aomhilite_contactform.htm
Although it appears at the top of the add-ons manager page (rather than being a toolbar button), the autocomplete listbox (https://addons.cdn.mozilla.net/user-media/previews/full/67/67103.png) also provides a dropdown arrow, which when clicked shows a dropdown list of your add-ons, from which you can select by clicking. The listbox can be turned on/off by the 'Select Add-on' List item in Addons Manager Hilite Options. Also make sure you are using the current version 2.1.1 to insure proper functioning of the listbox on Firefox 31 and newer.
When you have so many add-ons this thing is awesome. Especially because by default it's sorted by enabled/disabled. And this has an option to go alpha only. But I like the enabled/disabled, so this higlight feature comes in way handy. Especially for add-on devs.
Fetaure request: When it rehighlights can you also make it try to remember the scroll position as best as possible?
Yes! I thought I was the only one that noticed this annoying issue in FF4. I hate when I'm reading the details of an add-on near the bottom of the menu and then when I go back it resets to the top! Can't believe nobody from Mozilla had a problem with this. Thanks firefox lady!!